fix: lookbehind reporting

README.md

@@ -45,18 +45,30 @@ The constructor may throw:
 
 - `matches`: Returns the number of matches found.
 
+#### Callback Parameters
+
+- `isMatch` (boolean): Indicates whether a match was found.
+- `startIndex` (number): The start index of the data that doesn't contain the pattern.
+- `endIndex` (number): The end index (exclusive) of the data that doesn't contain the pattern.
+- `lookbehindBuffer` (Uint8Array | null): Buffer containing data from previous chunks that might be part of a match.
+- `currentBuffer` (Uint8Array | null): The current buffer being processed.
+
+Note:
+
+- The callback will contain EITHER the `lookbehindBuffer` OR the `currentBuffer`, not both at the same time.
+
 ## Usage
 
 ```js
 import { Match } from "gmatch";
 
 const matcher = new Match(
   "example",
-  (isMatch, bufferIndex, matchIndex, lookbehind, currentBuffer) => {
+  (isMatch, startIndex, endIndex, lookbehindBuffer, currentBuffer) => {
     if (isMatch) {
-      console.log(`Match found at index: ${matchIndex}`);
+      console.log(`Match found at index: ${endIndex}`);
     } else {
-      console.log(`Processed ${matchIndex - bufferIndex} bytes`);
+      console.log(`Processed ${endIndex - startIndex} bytes`);
     }
   },
 );
@@ -89,6 +101,6 @@ gmatch matches: 12
 streamsearch matches: 12
 ```
 
-## Acknowledgment
+## Acknowledgments
 
 Inspired by the excellent streamsearch package, both of which implement [FooBarWidget's streaming Boyer-Moore-Horspool algorithm](https://github.com/FooBarWidget/boyer-moore-horspool/blob/10e25ed66f7184a982fbe9239a8f46ac4969643c/StreamBoyerMooreHorspool.h).

src/index.js

@@ -110,7 +110,7 @@ const Match = class {
       if (index < 0) {
         const bytesToCutOff = this.#lookbehindSize + index;
 
-        if (bytesToCutOff > 0) {
+        if (bytesToCutOff) {
           this.#callback(false, 0, bytesToCutOff, this.#lookbehind, null);
         }
 
@@ -152,6 +152,13 @@ const Match = class {
       index += this.#skip[char];
     }
 
+    while (
+      index < buffer.length &&
+      !bufferCompare(buffer, index, this.#pattern, 0, buffer.length - index)
+    ) {
+      ++index;
+    }
+
     if (index < buffer.length) {
       this.#lookbehind.set(buffer.subarray(index));
       this.#lookbehindSize = buffer.length - index;

test/index.js

@@ -252,3 +252,41 @@ test("lookbehind test", (t, done) => {
   match.write("Te");
   match.write("failgreat");
 });
+
+test("pattern test", (t, done) => {
+  let count = 0;
+
+  const match = new Match("Hello, World!", (isMatch, start, end, l) => {
+    ++count;
+
+    if (count === 1) {
+      assert.strictEqual(isMatch, false);
+      assert.strictEqual(start, 0);
+      assert.strictEqual(end, 1);
+      assert.strictEqual(l, null);
+      done();
+    }
+  });
+
+  match.write("sHello, ");
+  match.write("World!");
+});
+
+test("pattern test", (t, done) => {
+  let count = 0;
+
+  const match = new Match("Hello, World!", (isMatch, start, end, l) => {
+    ++count;
+
+    if (count === 1) {
+      assert.strictEqual(isMatch, false);
+      assert.strictEqual(start, 0);
+      assert.strictEqual(end, 1);
+      assert.strictEqual(l, null);
+      done();
+    }
+  });
+
+  match.write("sHello, ");
+  match.write("World!");
+});